OPINION
BAKER, Judge.
Appellants-respondents Indiana Bell Telephone Company (SBC), Verizon North, Inc., and Contel of the South, Inc., d/b/a Verizon North Systems (Verizon) appeal the findings of the full board (Board) of the Indiana Utilities Regulatory Commission (IURC) in favor of appellee-peti-tioner the Indiana Payphone Association (IPA). Specifically, the Appellants argue that the Board erred in applying the New Services Test (the Test) to Verizon, in finding that Verizon did not take the sub-seriber line charge, also known as the end user common line charges (collectively, "Charges", into account in determining its revenue requirement, in recognizing findings from a separate proceeding, in ordering the Appellants to refund the Charges, [360]*360in not limiting the refund of the Charges to two years, and in reducing the prospective payphone rates. In its appellee's brief, the IPA asserts that the IURC erred in failing to order SBC and Verizon to pay interest on the refund of the Charges.
FACTS
The IPA is an organization of businesses that provide pay telephone service to the public by purchasing telephone lines and other services from local exchange companies like SBC and Verizon (collectively, "Locals"). In 1996, Congress passed the Telecommunications Act (the Act), which created a new regulatory scheme designed to "promote competition among payphone service providers and promote the widespread deployment of payphone services to the benefit of the general public" by replacing a state-regulated monopoly system with a federally-facilitated, competitive market. 47 U.S.C. §§ 251, 276.
In 1996, the Federal Communications Commission (FCC) issued a series of orders clarifying and implementing the Act. When presented with a matter from the Wisconsin Public Service Commission, the FCC took the opportunity to clarify how state commissions were to implement the Test (the Second Wisconsin Order). The Second Wisconsin Order, which was issued on January 31, 2002, noted the "longstanding precedent that [the FCC used] forward looking cost methodologies where [it] applied the [Test]." Appellee's Add., tab 2, para. 8. The Second Wisconsin Order also confirmed that rates for payphone service must comply with the Test, which allows the Locals to charge IPA only for the Locals' forward-looking costs. The Test is a cost-based test that sets the direct cost of providing the new service as a price floor and then adds a reasonable amount of overhead to derive the overall price of the new service. To this end, forward-looking, direct cost methodologies, such as total service long-run incremental cost (TSLRIC) or total element long-run incremental cost (TELRIC) should be used to calculate direct costs. The Second Wisconsin Order also noted the FCC's requirement that the Charges must be deducted from payphone rates to avoid double recovery by the Locals. The FCC also noted that the Test was required statutorily only for Bell Operating Companies (BOCs), but encouraged states to apply the Test more broadly, "thereby extending the pro-competitive regime intended by Congress to apply to the BOCs to other [Locals] that occupy a similarly dominant position in the provision of payphone lines." Appellee's Add., tab 2, para. 42.
On April 15, 1997, the IPA filed the first proceeding with the IURC, in which the IURC approved rates and charges for the Locals' payphone services in compliance with the Test. In the first proceeding, the IPA argued that the Charges were not lawful. The IURC did not rule on this issue, instead noting that the Charges "are the subject of a separate docket before this Commission docketed as Cause No. 41100 [the second proceeding]...." SBC's App. p. 112. The second proceeding, in which the IPA alleged that the Locals unlawfully collected the Charges and therefore owed a refund to the IPA, had been filed during the pendency of the first proceeding. The Locals filed tariffs and charged payphone rates in accordance with the final orders in the first proceeding.
After the issuance of the Second Wisconsin Order, the IPA filed a new complaint with the IURC on October 10, 2002 (the third proceeding). The IPA asked the IURC to set new, reduced future payphone rates and to direct the Locals to refund with interest to IPA members the difference between the requested new [361]*361rates and the existing, tariffed rates approved by the IURC in the first proceeding, retroactive to April 1997, when the first proceeding was filed. The IURC found, "In light of the FCC's recent reevaluation of the [Test] in [the Second Wisconsin Order], the Presiding Officers find that this is an appropriate time to review [the Locals'] rates." Appellee's App. p. 134.
On August 12 and 18, 2008, the IURC conducted an evidentiary hearing in the third proceeding. On September 29, 2004, the IURC issued its final order, finding:
1. SBC's rates for payphone access lines and features are hereby revised in accordance with the findings herein. SBC shall file tariffs in compliance with the findings within thirty (80) days of the date of the Order.
2. Verizon's rates for payphone access lines and features are hereby revised in accordance with the findings herein. Verizon shall submit proposed tariffs and supporting cost documentation in compliance with the findings within thirty (80) days of the date of the Order.
3. SBC's and Verizon's rates approved in [the first proceeding] should be adjusted for intrastate and or interstate subscriber line charges. Therefore, SBC and Verizon shall refund an amount equal to subsecriber line charges assessed since April 15, 1997 to present. The refunds shall be issued within ninety (90) days of the date of this Order and shall be issued in the form of a Tump-sum payment to each affected customer, and not in the form of a bill credit.
4. The IPA failed to prove that basic rates approved by the [IURC] in [the first proceeding] were unlawful and, with the exception of subscriber line charges, the IPA shall not be entitled to a refund of the difference between the rates approved in this Order and the rates approved in [the first proceeding].
5. This Order shall be effective on and after the date of its approval.
SBC's App. p. 40-41. The order made no mention of interest with the refund of the Charges. The IURC issued its final order on the second proceeding on the same day. On October 19, 2004, the Locals petitioned for reconsideration of the final order in the third proceeding, and on January 5, 2005, the petitions for reconsideration were deemed denied. The Locals now appeal.
DISCUSSION AND DECISION
The Locals contend that the IURC erred in applying the Test to Verizon because it is not a BOC, in finding that Verizon did not take the Charges into account in determining its revenue requirement, in recognizing findings in the second proceeding regarding the issue of whether the Charges were lawful, in ordering the Locals to refund the Charges, in not limiting the refund of the Charges to two years in accordance with a prior FCC decision, and in reducing the prospective payphone rates. On cross-appeal, the IPA argues that the IURC erred in failing to order the Locals to pay interest on the refund of the Charges because the IURC is authorized to award interest.
I. Standard of Review
The IURC is a fact-finding body with technical expertise to administer the regulatory scheme devised by the legislature. U.S. Gypsum v. Ind. Gas Co., 735 N.E.2d 790, 795 (Ind.2000); Ind.Code § 8-1-1-5.[362]*3621 The purpose of the IURC is to ensure that public utilities provide constant, reliable, and efficient service to the citizens of Indiana. Ind. Bell Tel. Co., Inc. v. Ind. Util Regulatory Comm'n, 715 N.E.2d 351, 354 n. 3 (Ind.1999). Our Supreme Court succinetly set forth the standard of review of IURC decisions as follows: ’
An order of the [IURC] is subject to appellate review to determine whether it is supported by specific findings of fact and by sufficient evidence, as well as to determine whether the order is contrary to law. On matters within its jurisdiction, the [IURC] enjoys wide discretion. The IURC's findings and decision will not be lightly overridden just because we might reach a contrary opinion on the same evidence.
U.S. Gypsum, 735 N.E.2d at 795. In order for this court to vacate the IURC's Order, the Locals must demonstrate that the order either lacks a factual basis or is contrary to law. Cellco P'ship v. Ind. Util. Regulatory Comm'n, 810 N.E2d 1137, 1142 (Ind.Ct.App.2004).
II. Application of the Test to Verizon
Verizon argues that as a non-BOGC, the IURC was without authority to apply the Test to its rates. The nondiscrimination safeguards in section 276 of the Act require only that the Test be applied to BOCs, like SBC. The Second Wisconsin Order noted that section 276 was enacted to "eliminate all discrimination between [BOC] and independent payphones and all subsidies or cost recovery for BOC payphones." Appellee's Add., tab 2, para. 2. Later in the Second Wisconsin Order, the FCC noted that it did not have a Congressional grant of jurisdiction over non-BOC Locals, but "[wle do, however, encourage states to apply the [Test] to all [Locals], thereby extending the pro-competitive regime intended by Congress to apply to the BOCs to other [Locals] that occupy a similarly dominant position in the provision of payphone lines." Appellee's Add., tab 2, para. 42. So while the FCC may be without authority to apply the Test to Verizon, state agencies like the IURC are encouraged to do so. The question then becomes whether the IURC has authority under Indiana law to apply the Test to Verizon.
The IURC's statutory authority to regulate intrastate telecommunications rates and charges stems from Indiana Code seetion 8-1-2-4, which states that "The charge made by any public utility for any service rendered or to be rendered either directly or in connection therewith shall be reasonable and just, and every unjust or unreasonable charge for such service is prohibited and declared unlawful." Under the traditional ratemaking methodology, the IURC must first find that a utility's existing rates are unjust and unreasonable; if it does, the IURC may then order just and reasonable rates to be charged in the future. Ind. Bell Tel. Co. v. Office of Util Consumer Counselor, 717 N.E.2d 613, 621-22 (Ind.Ct.App.1999), modified on rehearing on other grounds, 725 N.E.2d 432 (Ind.Ct.App.2000).
Here, the IURC found Verizon's rates to be unreasonable and therefore adjusted them in the third proceeding. SBC's Br. p. 68, 70-72. The next step is to order a just and reasonable rate, which the IURC determined could be reached through the application of the Test. Verizon does not argue that it is not in a "similarly dominant position" to the BOCs, and all evidence points to the conclusion that it is, in fact, similarly dominant. Therefore, we cannot say that the IURC erred in applying the Test to Verizon.
[363]*363III. Findings on the Charges
Verizon next argues that the IURC erred in finding that Verizon had not taken the Charges into consideration in determining its revenue requirement. Verizon challenges the following statement in the IURC's final order; "The evidence indicates that the total, jurisdictionally unsep-arated, cost of the local loop has not been reduced by the amount of the [Charges] for either SBC or Verizon, as required by the FCC." SBC's Br. p. 78.
In support of its contention that it did take the Charges into consideration, Verizon points us to Confidential Exhibit DLB~-1. This exhibit was introduced during the testimony of Verizon's first witness, David Behrle. Tr. p. 98. However, the TURC found that "[the data used in Mr. Behrle's and Mr. Dye's testimony is not the type of cost information upon which we believe accurate rates could be based." SBC's Br. p. 67. The IURC then ordered Verizon to provide additional cost support for its rates, and Verizon produced seven exhibits in response. Verizon does not contend that any of these additional exhibits support its argument that it took the Charges into consideration in determining its revenue requirement. We will not substitute our judgment on complex evidentiary issues and policy determinations that are better decided by an agency with technical expertise. Nextel West Corp. v. Ind. Util Regulatory Comm'n, 831 N.E.2d 134, 144 (Ind.Ct.App.2005). Because we will not substitute our judgment for the IURC's determination that Confidential Exhibit DLB-~1 does not contain information that will yield an accurate result and because there appears to be no other evidence in the record that Verizon took the Charges into account, we do not find any error in the IURC's conclusion that Verizon had not done so.
IV. Recognition of Findings in Second Proceeding
Verizon argues that the IURC erred in considering in the third proceeding its findings in the second proceeding regarding the Charges. Specifically, Verizon alleges that the IURC subsumed the issue of the Charges from the second proceeding into the third proceeding.
Verizon contends that the second proceeding is unrelated to the third proceeding because the second proceeding dealt only with the Charges from either 1984 or 1988 through April 15, 1997, but not thereafter. While it is true that in its motion for judgment on the pleadings, the IPA said that the charges were unlawfully collected between 1988 and April 15, 1997, it would be elevating form over substance to say that the Charges were not generally at issue. In the second proceeding, the IPA's complaint alleged that it was "entitled to a refund of all intrastate [Charges] imposed on them and collected by all [Locals] in Indiana." SBC's App. p. 354.
Furthermore, it is not uncommon or unlawful for the IURC to defer an issue from another related cause for resolution. We upheld a similar deferral of rate refund issues in Indiana Gas Co., Inc. v. Office of the Utility Consumer Counselor, 610 N.E.2d 865, 870-71 (Ind.Ct.App.1993). The IPA has consistently raised the issue of the lawfulness of the Charges throughout all three of the relevant proceedings at issue here. In the first proceeding, the IURC deferred the issue by noting that it would not address the subject of the Charges because they "are the subject of a separate docket before this Commission docketed as Cause No. 41100 [the second SBC's App. p. 112. We find this language to be sufficient to leave open the final determination of the issue of the Charges pending resolution of the issues in the other proceedings. For the [364]*364sake of administrative economy, the IURC ruled once and finally on the issue in the third proceeding. We do not find error in its having done so.
V. Refund of the Charges
The Locals next contend that the IURC erred in ordering a refund of the Charges. Specifically, they argue that a refund of the interstate Charges was not within the IURC's jurisdiction and that this action was effectively a retroactive rate reduction.
A. Jurisdictional Argument
Verizon contends, and the IURC does not dispute, that the ITURC has jurisdiction only over certain intrastate-not interstate-regulated services provided under tariffs filed with the IURC in Indiana. See G. Ittenbach Co. v. Cleveland, CC. & St. L. Ry. Co., 97 Ind.App. 332, 181 N.E. 382 (1932). Verizon complains of a statement in the final order for the third proceeding, in which the IURC ordered that "SBC's and Verizon's rates approved in [the first proceeding] should be adjusted for intrastate and or interstate subscriber line charges." SBC's App. p. 41.
In evaluating the issue of intrastate rates charged for payphone services in the Second Wisconsin Order, the FCC stated:
Under the [Test], the BOC may not charge more for payphone line service than is necessary to recover from PSPs all monthly recurring direct and overhead costs incurred by BOCs in providing payphone lines. The forward-looking cost studies used to make these determinations are usually calculations of total costs, not jurisdictionally separated costs. If an incumbent BOC files in its state tariff a charge that fully recovers these unseparated costs and also assesses on the PSP its federally tariffed [Charges], the BOC will over-recover its costs, and the PSP will over-pay in violation of the [Test] and the cost-based rates requirement of the Payphone Orders.
Appellee's Add., tab 2, para. 60 (emphasis added). In other words, where, as here, the TSLRIC or TELRIC study includes both interstate and intrastate costs, the Locals would recover those costs both through federal tariffs and through the intrastate rates. This is an impermissible double recovery that the Test seeks to avoid. So the IURC was not ordering a refund of interstate charges over which it had no jurisdiction, but was ordering the Locals to reduce an intrastate payphone charge by an amount equal to the federally-tariffed Charge. We do not find error in its having done so.
B. Retroactive Rate Reduction
We acknowledge that the IURC does not have authority to set rates retroactively; however, the grant of a refund does not necessarily amount to retroactive ratemaking. Airco Indus. Gases v. Ind.Mich. Power Co., 614 N.E.2d 951, 953 (Ind.Ct.App.1993). Because the IURC has only that power bestowed upon it by statute, the question is whether there is statutory authority that would allow it to order the refund of the Charges. Indiana Code section 8-1-2-68 states that when "the commission shall find any ... charges ... to be unjust, unreasonable, insufficient, or unjustly discriminatory, ... the commission shall determine and by order fix just and reasonable ... charges ... to be imposed, observed, and followed in the future." The IURC therefore has jurisdiction to set the rate of these Charges.
In support of its argument, SBC points us to In re Petition for Expeditied Review of BellSouth Telecomms. Inc.'s Intrastate Tariffs for Pay-Telephone Access Servs., 2004 Fla. PUC, 2004 WL 1567321 (2004). In BeliSouth, the Florida Commission ex[365]*365plicitly rejected the view that the Second Wisconsin Order permitted a retroactive decrease of tariffed payphone rates set in prior commission proceedings. The Florida Commission stated, "the most significant factor in the determination of whether refunds may be ordered is the fact that the Commission's Final [payphone rate] Order was protested, but the protest was subsequently withdrawn and the Order went into effect as a final Order." Id.
While it is true that the first proceeding produced a final order regarding the rates to be charged, we have already determined that the Charges were not a part of that order. That being the case, the Locals were on notice that the Charges were still an open issue, unlike the charges at issue in BeliSouth The Locals were collecting the Charges in spite of the fact that they had not yet been set by the IURC, and it was therefore not retroactive ratemaking to order a refund of the Charges.
VI. Two-Year Inmitation on Refund
Verizon asserts that the IURC erred in ordering the Charges to be refunded back to April 15, 1997. Specifically, Verizon argues that the refund should be limited to two years, and this order provides for a refund of over more than eight years.
In Communications Vending Corp. of Arizona, Inc. v. Citizens Communications Co., the FCC held that the period of time for refunds under the payphone provisions of the Act is limited to two years prior to the filing of the complaint. 17 F.C.C.R 24201, 24221-22 (2002). The IPA counters that only the FCC-not the IURC-is bound by this limitation. We need not decide the merits of this argument though because the IPA first raised the issue of the Charges on April 15, 1997, in the first proceeding. As we have already found, the IURC deferred the issue from the first proceeding, and it was not decided through the other two proceedings until September 29, 2004. Thus, the issue of the Charges was raised in the complaint in the first proceeding, which was filed on April 15, 1997, and was pending until September 29, 2004. Assuming the limitation period applies here, the IURC had authority to provide a refund dating back to April 15, 1995. It was therefore within the province of the IURC to award the refund from April 15, 1997.
VII Prospective Rate Reduction
SBC next contends that the IURC erred in ordering a prospective reduction in its payphone rates. Specifically, SBC argues that the IURC erroneously based the rate reduction on evidence from another proceeding and that the IURC exeluded SBC's spare capacity costs.2
A. Evidence from Another Proceeding
In the order, the IURC noted that it had examined certain evidence that SBC had introduced in a separate proceeding (UNE Proceeding):
[Wle have compared the TSLRIC costs for the elements at issue in this proceeding with comparable elements found in SBC Indiana's TELRIC studies [in the UNE Proceeding]. We find the cost support to be reasonably comparable, and thus, we will use the cost support provided by SBC Indiana as the basis for our analysis in this proceeding.
[366]*366SBC's App. p. 32. The IURC also directed that the 21.86% shared and common cost markup fixed in the UNE Proceeding for pricing SBC's unbundled network elements [UNE] would be used as the overhead loading percentage in setting the prospective payphone rates in this proceeding.
SBC argues that it was prejudiced by the denial of the opportunity to review the IURC's comparison. But we cannot see how that is the case. The IURC clearly stated in the order that it considered the TSLRIC cost studies submitted by SBC in this proceeding to be flawed in several respects. SBC's App. p. 32. For that reason, the IURC attempted to substantiate the validity of that TSLRIC study. And the IURC did ultimately use the TSLRIC study that SBC propounded in the present proceeding as the basis for its analysis here because it found the results to be valid based on the comparison. Id. Thus, the IURC did exactly as SBC hoped by submitting the evidence when it relied on the TSLRIC study, and SBC was not prejudiced by any comparison to the TEL-RIC study from the UNE Proceeding.
B. Spare Capacity Costs
SBC avers that the IURC's rate-fixing methodology excluded from consideration the spare capacity costs, The TSLRIC study did not include spare capacity costs, and the IURC accounted for this omission by determining that the 21.86% shared and common cost markup fixed in the UNE Proceeding would be used as the overhead loading percentage. SBC notes that its spare capacity costs were not included in the overhead costs in the UNE Proceeding, but were instead listed as direct costs. Thus, SBC concludes that the spare capacity costs were wrongly excluded from consideration.
The IPA counters that its expert testified that the TSLRIC and TEL-RIC results may or may not be different. Tr. p. 844. But IPA does not contend that the spare capacity costs were in fact included here. However, the IURC notes that we give great deference to its rate-making methodology. Office of Util. Consumer Counselor v. Gary-Hobart Water Corp., 650 N.E.2d 1201, 1204 (Ind.Ct.App.1995). The Test is a cost-based test that sets the direct cost of providing the new service as a price floor and then adds a reasonable amount of overhead to derive the overall price of the new service. Indiana Code section 8-1-2-4 requires that the rates set by the IURC be just and reasonable, not precise. As a court, we are "not concerned with the question of whether the rates or other orders of the commission are exactly those indicated by the evidence taken before the commission, nor with the question of whether they are the rates and orders which the court would have made...." Pub. Serv. Comm'n of Ind. v. City of LaPorte, 207 Ind. 462, 466, 193 N.E. 668, 670 (1935). SBC has not presented us with any argument or evidence as to why the prospective rate is unjust or unreasonable because of the exclusion of the spare capacity costs. As such, we will not second-guess the IURC's judgment in its ratemaking methodology.
VIII. Cross-Appeal-Interest on Refund
On eross-appeal, the IPA asserts that it is entitled to interest on the ordered refund of the Charges. The IPA requested an award of interest at the administrative level, and the IURC acknowledged that request in its order. SBC's Br. p. 49. In support of its position, the IPA points to the third in a trilogy of cases-Northern Indiana Public Service Company v. Citizens Action Coalition of Indiana, 548 N.E.2d 153 (Ind.1989) ("NIPSCO III"). In NIPSCO III, the TURC had ordered NIPSCO to pay a refund of certain charges plus interest at the rate of 6% [367]*367from the date of the final amended order. On appeal, the Citizens Action Coalition (CAC) challenged the 6% interest rate. Our Supreme Court found that the IURC has the inherent authority to make an award with interest and determined that "the statutory rate set forth in 24-4.6-1-103, provides, in this instance, a reasonable gauge of a fair return on one's funds when held by another." Id. at 161.
At issue in NIPSCO IIL was whether the statutes creating the IURC had abrogated the statutory and common law right to receive interest on money owed. Our Supreme Court held the statutes had not, such that the IURC had the authority to award interest at the statutory rate of eight percent. Id. at 161. The NLIPSCO court did not say that the IURC had discretion to decide whether to award interest with the refund. Rather, the question was "whether the ratepayers can obtain relief from the commission for the interest owed them or whether they will be foreed to seek relief in a separate action at law." Id. at 160. Thus, the court was concerned with how the CAC was to receive the interest it had a right to receive:
Given [the] rule that fully compensating a claimant demands that interest be paid where the amount of damage is readily ascertainable as of a particular time, it is apparent that, a fortiori, where the common law action is for an amount of money owed, interest is recoverable as damages since its amount is obviously more "readily ascertainable" than in an action where the damages sought are for injury to property. It is clear then that, under common law, CAC could bring an action for the money NIPSCO owed them and receive, as part of its judgment, interest on the money withheld from the date of its payment and may also have a right to interest under I.C. 241-4.6-1-108. The amount paid here was clearly ascertainable and is not in dispute. Whether CAC retains this right to interest under the funds held by NIPSCO depends on whether the enabling legislation that empowers the commission has abrogated this right.
Id. (emphasis added). Thus, if the party requesting a refund from the IURC can demonstrate that "the amount of damage [was] readily ascertainable as of a particular time, ... interest is recoverable as damages." Id. Just as a jury would not have discretion to decline to award such interest, neither would the IURC. See id.
Here, SBC and Verizon were ordered to refund the Charges. If the amount of the Charges was "readily ascertainable" and "not in dispute," id., then the IURC was required to order SBC and Verizon to pay interest on those refunds from the collection date of the money to be refunded. We remand this cause, therefore, with instructions to determine whether the refund met these criteria and to enter an award of interest if appropriate.
The order of the TURC is affirmed in part and remanded with instructions to determine whether the amount of the Charges was readily ascertainable and not in dispute and to enter an award of interest if appropriate.
SULLIVAN, J., concurs.
MAY, J., concurs and dissents with opinion.